1. Field of the Invention
This invention relates to a method of making a magnetic recording medium such as a flexible magnetic disk. This invention particularly relates to a method of making a magnetic recording medium with high productivity, which efficiently carries out surface polishing, inspection for defects and punching out into a predetermined shape.
2. Description of the Prior Art
Floppy disks (FD) are widely used as external storage media for computers and word processors.
The floppy disks have heretofore been made by polishing the surfaces of disks punched out with a die into a ring-like shape from a strip-like substrate coated with a magnetic material and dried (hereinafter referred to simply as a film), and then subjecting the disks one by one to inspection for defects on the surfaces of the disks.
Polishing of the surface of the magnetic layer overlaid on the surface of the aforesaid film is carried out mainly for the purpose of eliminating defects such as protrusions on the surface. However, defects which cannot be removed only with the polishing often remain on the disks. Such defects give rise to recording failures or reproducing failures, and therefore the disks have to be inspected in an inspection step to find and eliminate those with defects. As the inspection method, the method as disclosed in Japanese Unexamined Patent Publication No. 59(1984)-52775 wherein recording and reproduction of a specific pattern are carried out by rotating the magnetic disks one by one is widely used. With the aforesaid method of making a floppy disk, since the surface polishing and the defect inspection are carried on the magnetic disks one by one after they are punched out into a ring-like shape, a long time is required for the operations, and productivity is low.
In order to solve the aforesaid problem, it has been proposed as disclosed in Japanese Unexamined Patent Publication No. 60(1985)-151838 to polish the surface of a strip-like film coated with a magnetic material by moving the film, and subsequently punch out the tape with a die into a predetermined shape to form floppy disks. With the proposed method, though the efficiency of the surface polishing step becomes high, a step of inspecting the floppy disks, which have been punched out into a predetermined shape, one by one for confirming whether defects are present on each floppy disk is necessary. In the inspecting step, inspection as in the conventional technique is carried out. Therefore, the productivity cannot be increased substantially.